Low pour vacuum gas oil compositions

ABSTRACT

A vacuum gas oil fuel composition suitable for pipeline transportation of substantially reduced pour point comprising a wax containing vacuum gas oil base stock having incorporated therein a minor amount of high asphaltene residuum such as an Arabian Light 1,050,*F. residuum and a pour depressing amount of an interpolymeric poly(n-alkylacrylate) of a molecular weight between about 3,000 and 100,000 wherein said alkyl is of at least 18 carbons and at least 70 wt. % of said alkyl is between about 20 and 24 carbons inclusively, the C20 to C24 alkyl group consisting of between about 2 and 65 wt. % of C20 alkyl, between about 18 and 65 wt. % C22 alkyl and between about 8 and 35 wt. % C24 alkyl.

United States Patent [191 Miller et al.

[ LOW POUR VACUUM GAS OIL COMPOSITIONS [75] Inventors: Kenneth D. Miller, Nederland; Levi C. Parker, Port Arthur, both of Tex.

[73] Assignee: Texaco, Inc., New York, NY.

[22] Filed: Nov. 8, 1972 [21] Appl. No.: 304,676

[52] US. Cl 44/62, 44/70, 44/80,

137/13 [51] Int. Cl C101 1/14 [58] Field of Search 44/62, 70, 80; 137/13 [56] References Cited UNITED STATES PATENTS 2,020,714 11/1935 Wulff et al. 252/56 R 2,091,627 8/1937 Bruson 252/56 R 2,891,991 6/1959 Stewart et al 44/70 X 2,917,375 12/1959 l-ludson..... 44/80 X 2,967,816 l/l96l Hudson 44/62 X FOREIGN PATENTS OR APPLICATIONS 6/1964 France 44/62 Dec. 10, 1974 Primary Examiner-Patrick P. Garvin Assistant Examiner-Andrew H. Metz Attorney, Agent, or FirmT. l-l. Whaley; C. G. Ries A vacuum gas oil fuel composition suitable for pipeline transportation of substantially reduced pour point comprising a wax containing vacuum gas oil base stock having incorporated therein a minor amount of high asphaltene residuum such as an Arabian Light 1,050,F. residuum and a pour depressing amount of an interpolymeric poly( n-alkylacrylate) of a molecular weight between about 3,000 and 100,000 wherein said alkyl isof at least 18 carbons and at least 70 wt. of said alkyl is between about 20 and 24 carbons inclusively, the C to C alkyl group consisting of between about 2 and 65 wt. of C alkyl, between about 18 and 65 wt. C alkyl and between about 8 and 35 wt. C alkyl.

ABSTRACT 2 Claims, No Drawings 7 1 LOW POUR VACUUM-GAS OIL COMPOSITIONS APPLICATION OF RELATED INTEREST Coassigned, copending application Ser. No. 266,839, filed June 27, 1972.

BACKGROUND OF INVENTION This invention relates to improved vacuum gas oil compositions of significantly reduced pour point and to transportation of these compositions in pipelines. More particularly, it pertains to vacuum gas oil compositions comprising a wax containing vacuum gas oil base stock. having a pour. depressing amount of an interpolymeric poly(n-alkylacrylate) and a minor amount of high asphaltene residuum incorporated therein.

Gas oils are generally defined in the petroleum industry as hydrocarbon fractions in a crude oil ranging between the kerosene fraction and the lubricating oil fraction. However, the boundaries of the gas oil fraction can overlap into adjacent fractions within the standard definition employed. The vacuum gasoils are normally the heavier, that is, higher boiling portions of the gas oil fraction being recovered asits name denotes under vacuum, e.g., 0.05'0.2 atmosphere.

Petroleum hydrocarbon oils employed in cold climates or exposed to low temperature frequently require the use of an additive to maintain their fluidity, e.g., in pipeline transportation, or to meet pour point specifications. Additives that are effective for this are called pour depressors. The art discloses numerous classes of pour depressors. v

Pour depressant additives are mostly high molecular weight organic compositions prepared by alkylation of benzene, naphthalene or derivatives thereof, by polymerization of low molecular weight methacrylates, and by the condensation polymerization of various types of these compounds. Many of these additives are not entirely suitable in vacuum gas oils because of their high cost, high concentration required or becausethey are relatively ineffective in reducing the pour point ofvacuumgas oil base stocks containing higher molecular weight waxes.

Although a wide variety of different pour depressants mentioned above are useful for incorporating in heating oils, diesel'fuels and many other liquid hydrocarbon oils, they havebeen found, in general, to be relatively ineffective in decreasing the pour point of vacuum gas oil base stocks containing the higher molecular weight waxes. The poor performance of these additives may result from the structural and/or molecular weight difference of waxes occurring in the various oil fractions.

In the past, two means which have been employed in attempting to improve the pour point characteristics of wax containing vacuum gas oils are the solvent extraction (dewaxing) process and the centrifugal dewaxing method. Solvent dewaxing involves introducing and recovering a large amount of valuable solvent material which necessarily results in an expensive operation. In the centrifugal method of separating the wax it is necessary to first add a cutter stock such as naphtha and then cool the gas oil mixture to a low temperature such as about 25F. which is time consuming and also a costly processing step. Still another approach called for -the thermocracking of the waxy vacuum gas oil base stocks. However, the thermocracking process, al-

though resulting in the reduction of the pour point of I gas oils at a reasonable cost. However, there is a continuing search 'to improve the effectiveness of this found interpolymeric poly(n-alkylacrylate) pour depressor.

A main object of the present-invention is to improve the pour point characteristics of Wax containing vacuum gas oils without utilizing elaborate and expensive solvent extraction or centrifugal dewaxing procedures.

Another object of this invention is to provide improved vacuum gas oil compositions prepared by incorporating therein a pour depressing amount of an oil soluble .interpolymeric poly(n-alkylacrylate) and a vacuum residuum of high asphaltene contentin a wax containing vacuum gas'oil.

Still another object'of the invention isto improve the wax containing vacuum gas oil base stocks so they may be handled, e.g., in pipeline transportation with greater easeand flexibility in climates where ambient temperatures are neartheir pour points.

SUMMARY OF INVENTION We have discovered and this constitutes our invention a vacuum gas oil fuel composition of reduced pour point comprising a vacuum gas oilhaving a wax content of between about 0.5 and 20 wt. and containing the pour reducing combination of between about 1 and 20 wt. of a high asphaltene containing petroleum residuum and between about 0.002 and 3 wt. of a pour depressing quantity of an oil soluble poly(nalkylacrylate) of a molecular weight between about 3,000 and 100,000 wherein said alkyl is of at least 18 carbons and at least wt. of said alkyl is about 20 to 24 carbons, the C to C n-alkyl group consisting of between about 2 and 65 wt. C alkyl, between about 18 and 65 wt. C alkyl and between about 8 and 35 wt. C alkyl.

In another aspect, this invention relates to a process for the pipeline transporation of the above mentioned fuel oil compositions.

Surprisingly, it has been found that the addition of a minor amount of a high asphaltene residuum together with a small amouht of an oil soluble poly(nalkylacrylate) to a vacuum gas oil or mixture of gas oils as defined yield a fuel oil composition of muchlower pour point than when either residuum or polyacrylate alone is added to the vacuum gas oil base stock. An unexpected synergistic action is achieved through the addition of the residuum together with the polyalkylacrylate interpolymer.

The waxy type vacuum gas oil base stocks contemplated herein have a wax content between about 0.5 and 20 wt. a pour point betweenabout 60 and lO0F.-, an atmospheric boiling point between about 450 and l,050F., an API gravity between about 20 and 35 and are normally derived from the distillation of crude oils such as Arabian Light crude oils at vacuum pressures ranging between about 0.05 to 0.2 atmospheres. Typical vacuum gas oils which may be employed are Desulfurized Arabian Light Vacuum Gas Oil (DS Arabian Lt. VGO), Desulfurized Lago Medio Vacuum Gas Oil (DS Lago Medio VGO), Arabian As heretofore stated, the pour point depressant additives useful in the practice of this invention are the gas oil soluble interpolymeric po1y(n-a1ky1acry1ate)s of a molecular weight between about 3.000 and 100.000.

about 1 to wt. based on the weight of the composition. lt isto be noted this residuum component not only synergistically enhances the pour depressing effect of the po1y(n-a1kylacrylate) pour depressor but also functions as a fuel that is an energy supplying ingredient. Suitable properties of typical residuous fractions which may be utilized in the novel compositions of this invention are set forth in Table 2 below:

TABLE 2 Light Vacuum Gas Oil (Arabian Lt. VGO), Lago 5 preferably between 4000 and 52.000. most preferably M di Va Ga Oil (La o M di VGO) d A between 15.000 and 35.000 wherein said alkyl is of at Vacuum gas oil, etc. whose physical properties ar t least 18 carbons, at least- 70 wt. of said alkyl is bet i T bl I as f ll tween and 24 carbons inclusively. the C to C 24 TABLE 1 Amna Vac. D.S. Lt. D.S. Lago Lago Medio Arab. Lt. (MS 011. Gas 011 Arab. voo Medio V00 V00 V00 Boiling Range. F. 650-900 650-1050 650-1050 450-1050 650-1050 Pour Point. F. (ASTM D-97) +95 +90 +90 +90 95 Sulfur. wt. '76 0.30 0.23 0.16 1.4 2.6 Wax Content. wt. 7: 17.3 -11 -10 -10 -11 Kin. Visc. at 122F.. cs. 1 1.5 37.2 27.0 Kin. Viscfat lF.. cs. l6.2 58.0 APl Gravity. 60F. 32.6 25.5 28.1 27.0 20.0 Gas Oil Distillation. Vol. '70 Recovered at F 0. o 587F. 453538F. 68|-749F. 10-20 636-698 586-642 773-804 30-40 708-734 689-743 825-848 50 750 778 868+ 60-70 771-796 810-855 80-90 823-858 882+ 95 EP? 876-899 nap 11111131 Boiling 1.1.. "E? End Point The high asphaltene residuum component suitable 30 alkyl group consisting of between about 2 and 65 wt. for use in the fuel oil compositions of this invention in-. of C alkyl, between about 18 and 65 wt. C a1- clude a wide variety of residual fuel oil bottoms such as kyl, and between about 8 and wt. C alkyl. The Arabian Light (650F. or greater) residuum, Lago interpolymers are derived from standard polymeriza- Medio (650F. or greater), a thermally cracked tion techniques such as polymerizing the alkylacrylate heavy fraction of Amna Crude (650F. or greater), 35 monomers in the presence of acrylate polymerization West Texas Sour Residuum (650F. or greater) and catalyst, e.g., azo catalyst such as azobisisobutronitrile thermal cycle fuel oil from various crude sources. Prefdescribed in US. Pat. No. 2,471 ,959,or the well known erably, the residuous stocks employed will have an asperoxide catalysts such as benzoyl peroxide and lauroyl phaltene content of about 4 to about '15 wt. and a peroxide, utili'zingcatalyst quantities of between about carbon residue of about 5 to 25 wt. Gravity of the 0.1 and 5 wt. Polymerization is normally conducted residuous stocks will range from about 5 to about 20 at a temperature between about and 150C., prefer- APl (F Although the amount of residuum 1n the ably at -l00C.,' utilizing a nitrogen blanket to prefuel oilcompositions of this invention can be varied vent oxidation-of the catalyst. During polymerization over a wide range, the maximum amount which can be normally a periodic sample is taken for refractive index utilized is about 20 wt. and preferably will be from 45 (R1) determination. The polymerization reaction is continued until the refractive index remains steady. The reaction time is normally between about 1 and 10 hours.

The n-alkylacrylate monomers from which the interpolymeric poly(n-alkylacrylate) products are prepared are made by standard esterification techniques through the reaction of acrylic acid with n-alkanol mixtures wherein the reactive n-alkanols in said mixture have at Tests on Residue Stocks nsoluble. wt.

' 1050F. 900F. 1050F. Cracked Thermal Cycle Lago Medio Amna Arab 950F.

Fuel Oil Resid. Resid. Lt.Resic1. Amna Crude Pour Point. F. +35 120+ 12 +70 Sulfur, wt. 7: 0.87 2.8- 0.31 3.2 0.29 Vis. Kin.. at 122F. cs. 392 Vis. Kin.,.at 210F. cs. 46.2 1700 23.9 at 300F. 469 API Gravity. at 60F. 8.0 9.8 14.8 9.2 Carbon Residue. wt.'% 20.4 17.5 17.1 As haltene basis N-C, 12 9 9 least 18 carbons and 70 wt. thereof are in the nalkanol group of'20 to 24 carbon atoms, said group consisting of between about 2 and 65 wt. of eicosanol, between about 18 and 65 wt. of docosanol and between 8 and 35 wt. tetracosanol. One suitable source of alcohol mixtures are the alcohols sold under the tradename Alfols by Continental Oil Co. Alfols are impure mixtures of n-alkanols of various chain lengths, the remainder consisting of hydrocarbons, ketones and hindered unreactive alcohols. Typical analysis of two suitable examples of the Alfol alcohols are as follows:

Color. Gardner 12 18 A standard means of acrylate monomer precursor preparation is reacting (esterifying) the alcohol mixture with acrylic acid in the presence of an esteritication catalyst such as p-toluenesulfonic acid and a polymerization inhibitor, e.g., hydroquinone desirably in the presence of an azeotroping agentfor water byproduct removal such as benzene. The esterification is conducted, for example. at a temperature between about 190 and 200F. and is continued until the amount of water by-product is removed as overhead indicating that the esterification is essentially complete.

The novel fuel compositions of this invention can be prepared in a variety of ways. For example, the residuum component can be mixed with the base vacuum gas oil or gas oils and the polyacrylate can be admixed as a solution in toluene, xylene, light lube oil or in the vacuum gas oil itself. One preferred solvent to facilitate introduction of the polyacrylate pour depressor into the vacuum gas oil base stock is a solvent such as a light lubricating oil of a kinematic viscosity of between about 2 and 4 cs. at 100F. to form between about and 50 wt. polyacrylate lube oil concentrate.

Generally, the residuum and gas oil components are heated to a temperature of about 175 to 300F., preferably at 175 to 250F. prior to the addition of the polyacrylate following which addition the resulting mixture is heated at a temperature of about 175 to 300F., preferably 175 to 250F., for about 0.2 to 1.5 hours or more to insure complete solution of the interpolymeric blend. It is important that the polyacrylate pour depressor be introduced at a temperature above the solution point of the wax component. 1f the polyacrylate is mixed with a vacuum gas oil at a temperature substantially below the solution point of a substantial portion of the wax component, there is little or no pour depressing effect afforded by the polyacrylate-- residuum combination.

' positions described in detail above.

The improved process of this invention for the pipeline transportation of viscous fuel oils comprises introducing into the pipeline a fuel oil composition comprising a major amount of vacuum gas oil boiling between 450 and 1,050F. and a minor amount (i.e. not over 20 percent by weight and preferably about 1 to about 15 wt. based on the weight of the composition) of a high asphaltene residuum and an effective pour depressant amount of a poly(n-alkylacrylate) as heretofore described.

The following examples further illustrate the invention but are not to be construed as limitations thereof.

EXAMPLE I This example describes two species of the po1y(nalkylacrylate), Polyacrylate A and B, contemplated herein and their method of preparation.

Polyacrylates a and B are described and prepared as follows:

Monomer Synthesis g The alcohols employed to prepare the A and B monomers were as follows:

Typical Properties Alcohol B rived Mono-Acrylate A and B as follows:

Material Wt. (g).

Hydroquinone 2 0.02 p-Toluenesulfonic acid 5.6 0.036 Alcohol A 952 2 Alcohol B 1245 2 Acrylic acid, glacial 144 2 Benzene 536 All the above charge except the acrylic acid was put together under nitrogen at about 60C. (140F.). The acrylic acid was then added with stirring and the mixture brought to reflux, with a pot temperature of about C. (194F.). Nitrogen was introduced below the surface of the liquid reaction mixture at a rate of between about 40 and 45 m1s./minute as the water of reaction was azeotroped off at a reflux rate of 4 mls./minute.

About 96 percent of the theoretical amount of water was removed in 12 hours and all the water was removed in 21 hours. Benzene was removed by stripping the product to 15 mm Hg pressure at a pot temperature of about 60C. (140F.). Physical data for the monomer product was as follows:

8 I A series of blends was prepared utilizing desulfurized heavy vacuum gas oil as the base stock and Arabian Light 1,050F. plus residuum by mixing the two compo- Mono- Mono- Physical Data for Monomer Acrylate A Acrylate B nents at 200 F. for 30 minutes; The polyacrylate coma ponent employed was Polyacrylate A described in Exa ample I. Polyacrylate A (PAA) was introduced into the Hydroxyl No. 8 14 base stock and residuum mixture at 200F. The out- 3 332223223 f-fig 5-33%? standing reductions in.pour points as well as the syner- Kim vise grstrc action achieved through the Polyacrylate- 150F. 7.39 8.84 residuum combination can be seen in the followin tag 2 10 F. 7 3.9 4.5 0 bles 1a sts es ue, Meliing Point, C. 0 36 33 Following Table 3 describes the vacuum gas 011 base and B were heated in separate runs to 85C. (185F.)

over a minute period under prepurified nitrogen introduced into the reaction system at a rate of 120 mls/minute. The nitrogen flow was then reduced to 40 mIsJminuteand 4 grams of azobisisobutronitrile were added. The reaction mixture was stirred and readings of the refractive index of the mixture were taken at hour intervals, and the reaction was continued until the refractive index is constant, that is, :t 3 units in the fourth decimal place. The total reaction time required was about 1.5 hours.

The product was cooled and analyzed and the resultant polyacrylates gave the following analysis:

stock and the vacuum residuum employed and Table 4 sets forth pour depressing data. Blends D, F and H are representative of the compositions of the invention and Blends A, C, E and G are comparative blends. As can be seen by subsequent Table 4, when only vacuum residuum is employed as the pour depressing ingredient even in amount of 10 wt. essentially no pour depression takes place. When the polyacrylate is'employed as the sole pour depressor at 0.1 wt. amount the pour depression is about 15F. However, when the combination of residuum and polyacrylate is employed the average pour depression is about F. Fuel oils of the type presented in Table 4 normally carry an ASTM pour requirement of +60F. maximum. As can be seen, addition of the residuum alone produces essentially no pour reduction in the vacuum gas oil. Addition of the pour depressor alone brought the pour to +6065F., which is borderline to failing. The synergistic effect of adding residuum and pour depressor to the vacuum gas oil reduced the pour point to about 50F., well within pour point specification.

Physical Data Polyacrylate a Polyacrylate B TABLE 3 R1 1.4545 1.4540 Y Sp. Grav., lF./60F. 0.8580 0.8495 Melting Point, C. 47 48 Test Results on Component Stocks Kin. Visc., cs 150F. 196 11.5

210F. 81 49 Arabian Lt. Arabian Dialysis, 7a Residue 48 Desulfurized Lt. Vac. M0. Residue 23.000 20000 Stock Hvy. Vac. Gas Oil Residuum Gravity, API 28.2 Sp. Grav., at /60F. 1.013 Kin. Visc., cs. at EXAMPLE 100:F (SUS) 37.73 (176) This example illustrates the composition of the inven- E 3 6 tion, the outstanding pour depressing effect of the poly- 45 Pour, ASTM Upper, F. +80 +95 Sulfur, wt. (X-Ray) 0.20 3.9 acrylate and the residuum and their synergistic mterac Carbon Residue, wt. '94 tion to reduce pour.

TABLE 4 Enhancing Effectiveness of PAA Pour Depressant in Gas Oil Stock by Addition of Vacuum Residuum BLEND A B C D E F G H Arabian Lt. D5 100 100 90.0 90.0 95.0 95.0 97.5 97.5

HVGO, wt. 70 Arabian Lt. Vac.

Resid. wt..% 0 0 10.0 10.0 5.0 5.0 2.5 2.5 PAA, wt. None 0.10 None 0.10 None 0.10 None 0.10 Test Results our ornt, ASTM Upper +80 +75 +50 +80 +50 V Maximum +80 +60 +45 +75 +55 +75 +50 Kin. Visc., cs at Maximum pour point provides an indication of the stable pour point of a fuel oil. In the maximum determination, the gas test oil is heated to 220F. for about 30 minutes. following which it is cooled rapidly to 0F. by placing in a cold box. This low temperature nucleates the wax present. After 12 or more hours. the fuel oil is removed and allowed to warm at ambient temperature. An ASTM pour point is then obtained. Residual fuel oil blends containing distillate stocks sometimes exhibit pour reversion tendencies (pour increases) upon storage. The above blends containing PAA residuum showed no pour reversion characteristics.

We claim:

1. A vacuum gas oil fuel oil composition comprising a major amount of vacuum gas oil boiling between about 450 and 1,050F. and having a wax content between about 0.5 and 20 wt. containing 1). between about 1 and 20 wt. of an asphaltene petroleum residuum having an asphaltene content of between about 4 and 15 wt. and an API Gravity of between about and 20 and a carbon residue of between about 5 and 25 wt. and 2). between about 0.002 and 3 wt. of an interpolymeric poly(n-alkylacrylate) of amolecular weight between about 3,000 and 100,000 wherein said n-alkyl is at least 18 carbons and where at least 70 wt. of said n-alkyl is of 20 to 24 carbons consisting of between about 2 and 65 wt. C alkyl, between about 18 and 65 wt. C alkyl, and between about 8 and 35 wt. C alkyl, said p oly(n-alkylacrylate) incorporated in said base stock at a temperature above the solution point of said wax. a

2. In the pipeline transportation of viscous fuel oil the improvement which comprises introducing into the said pipeline a fuel composition comprising a major amount of vacuum gas oil boiling between about 450 and 1,050F. and having a wax content between about 0.5 and 20 wt. containing 1). between about l and 20 wt. of an asphaltene petroleum residuum having an asphaltene content of between about 4 and wt.

v and an API Gravity of between about 5 and and a carbon residue of between about 5 and 25 wt. and 2). between about 0.002 and 3 wt. of an interpolymeric poly(n-alkylacrylate) of a molecular weight between about 3,000 and 100,000 and wherein said nalkyl is at least 18 carbons and'where at least wt. of said n-alkyl is of 20 to 24 carbons consisting of be-. tween about 2 and 65 wt. C alkyl, betweem about 18 and 65 wt. C alkyl, and between about 8 and 35 wt. C alkyl, said poly(n-alkylacrylate) incorporated in said base stock at a temperature above the solution point of said wax. 

1. A VACUUM GAS OIL FUEL COMPOSITION COMPRISING A MAJOR AMOUNT OF VACUUM GAS OIL BOILING BETWEEN ABOUT 450* AND 1,050*F. AND HAVING A WAX CONTENT BETWEEN ABOUT 0.5 AND 20 WT,% CONTAINING 1). BETWEEN ABOUT 1 AND 20 WT. % OF AN ASPHALTENE PETROLEUM RESIDUUM HAVING AN ASPHALTENE CONTENT OF BETWEEN ABOUT 4 AND 15 WT. % AND ANAPI GRAVITY OF BETWEEN ABOUT 5* AND 20* AND A CARBON RESIDUE OF BETWEEN ABOUT 5 AND 25 WT % AND 2).BETWEEN ABOUT 0.002 AND 3 WT. % OF AN INTERPOLYMERIC POLY(N-ALKYLACRYLATE) OF A MOLECULAR WEIGHT BETWEEN ABOUT 3,00 AND 100,000 WHEREIN SAID N-ALKYL IS LEAST 18 CARBONS AND WHERE AT LEAST 70 WT. % OF SAID N-ALKYL IS OF 20 TO 24 CARBONS CONSISTING OF BETWEEN ABOUT 2 AND 65 WT. % C20 ALKYL, BETWEEN ABOUT 18 AND 65 WT. % C22 ALKYL, AND BETWEEN ABOUT 8 AND 35 WT. % C24 ALKYL, SAID POLY(NALKYLACRYLATE) INCORPORATED IN SAID BASE STOCK AT A TEMPERATURE ABOVE THE SOLUTION POINT OF SAID WAX.
 2. In the pipeline transportation of viscous fuel oil the improvement which comprises introducing into the said pipeline a fuel composition comprising a major amount of vacuum gas oil boiling between about 450* and 1,050*F. and having a wax content between about 0.5 and 20 wt. % containing 1). between about 1 and 20 wt. % of an asphaltene petroleum residuum having an asphaltene content of between about 4 and 15 wt. % and an API Gravity of between about 5* and 20* and a carbon residue of between about 5 and 25 wt. % and 2). between about 0.002 and 3 wt. % of an interpolymeric poly(n-alkylacrylate) of a molecular weight between about 3,000 and 100,000 and wherein said n-alkyl is at least 18 carbons and where at least 70 wt. % of said n-alkyl is of 20 to 24 carbons consisting of between about 2 and 65 wt. % C20 alkyl, betweem about 18 and 65 wt. % C22 alkyl, and between about 8 and 35 wt. % C24 alkyl, said poly(n-alkylacrylate) incorporated in said base stock at a temperature above the solution point of said wax. 